Transient damping means for an electrical installation

ABSTRACT

There is provided in accordance with an embodiment of the invention a wave trap assembly for connection in series with an electrical conductor means such as an electrical power transmission line for the purpose of attenuating or damping transient high frequency phenomena, and comprising a non-magnetic conductor member received in a slot in a stack of magnetic laminations, whereby the inductive effect of the magnetic laminations causes displacement of the high frequency transient currents into a reduced cross-sectional area of the conductor contiguous the outer periphery of the magnetic laminations, to modify the action of the normal high frequency skin effect whereby to more effectively attenuate the high frequency phenomena. The conductor may be cast in the slot. In a modified embodiment, the radially or peripherally outer portion of the conductor lying in the slot of the stack of magnetic laminations may be made of a higher resistance material than the radially inner portion of the conductor whereby to further attenuate high frequency transient currents flowing in the peripherally outer portion of the conductor. In a still further embodiment of a conductor lying in a slot in a stack of magnetic laminations, a radially inner conductor portion of larger cross section may be connected by a narrow cross-section neck portion to a radially outer conductor portion of smaller cross section than the radially inner conductor portion whereby to promote the transfer of high frequency transients to the outer portion. In another embodiment, the wave trap assembly may comprise a plurality of circumferentially spaced conductor members lying in slots in the peripheral surface of a drum-like stack of magnetic laminations. In still another embodiment, a plurality of wave trap assemblies may be supported by stand-off insulators and by conducting spacers in such manner as to be connected in series with each other and in series with the power transmission line.

United States Patent [191 Pflam:

[ TRANSIENT DAMPING MEANS FOR AN ELECTRICAL INSTALLATION [75] Inventor:Herbert M. Pflanz, Westwood,

Mass.

[73] Assignee: Allis-Chalmers Corporation,

Milwaukee, Wis. 53201 [22] Filed: Dec. 20, 1972 [21] Appl. No.: 316,985

[52] US. Cl. 333/12; 333/70 S; 333/81 R; 174/126 CP [51 Int. Cl. H04b3/28 [58] Field of Search 333/12, 81 R, 79, 70 S; 174/126 CS. 126 CL,2:178/45 [56] References Cited UNITED STATES PATENTS 499,852 6/1893Pfannkuche 178/45 X 657,196 9/1900 Guilleaume 178/45 3,292,072 12/1966Hylten-Cavallius et al 333/79 FOREIGN PATENTS OR APPLICATIONS 227,7146/1943 Germany 333/79 2,702 12/1918 Netherlands 174/126 CS 19,103 9/1899United Kingdom 178/45 Primary ExaminerAlfred E. Smith AssistantExaminer-Wm. H. Punter Attorney, Agent, or FirmRobert C. Sullivan [57]ABSTRACT There is provided in accordance with an embodiment of theinvention a wave trap assembly for connection in series with anelectrical conductor means such as an electrical power transmission linefor the purpose of [451 May 6,1975

attenuating or damping transient high frequency phenomena, andcomprising a non-magnetic conductor member received in a slot in a stackof magnetic laminations, whereby the inductive effect of the magneticlaminations causes displacement of the high frequency transient currentsinto a reduced cross-sectional area of the conductor contiguous theouter periphery of the magnetic laminations, to modify the action of thenormal high frequency skin effect whereby to more effectively attenuatethe high frequency phenomena. The conductor may be cast in the slot. Ina modified embodiment, the radially or peripherally outer portion of theconductor lying in the slot of the stack of magnetic laminations may bemade of a higher resistance material than the radially inner portion ofthe conductor whereby to further attenuate high frequency transientcurrents flowing in the peripherally outer portion of the conductor. Ina still further embodiment of a conductor lying in a slot in a stack ofmagnetic laminations, a radially inner conductor portion of larger crosssection may be connected by a narrow crosssection neck portion to aradially outer conductor portion of smaller cross section than theradially inner conductor portion whereby to promote the transfer of highfrequency transients to the outer portion. In another embodiment, thewave trap assembly may comprise a plurality of circumferentially spacedconductor members lying in slots in the peripheral surface of adrum-like stack of magnetic laminations. In still another embodiment, aplurality of wave trap assemblies may be supported by stand-offinsulators and by conducting spacers in such manner as to be connectedin series with each other and in series with the power transmissionline.

25 Claims, 14 Drawing Figures Pmsmeumw 6l975 3.882.427

SHEET 10F 2 HlG/H FREQUENCY I8? H LOW FREQUENCY 20 E- iEIGHT vs CURRENTDISTR\BUTION \O' 9 0 AST C NDUCTOR PATENIEUMAY 61975 882.427 saw 2 OF 2W GENERATOR STEP DOWN STEP U TRANSFORMER TRANSFORMER 202 WAVE TRAP WAVETRAP 2 WAVE TRAP C IFZC U IT BREAKER 2K) cmcurr BREAKER LOAD *GENERATINGsTAT|oN+ |oo MILE TRANSMISSION LINE LOAD STATION 1 TRANSIENT DAMPINGMEANS FOR AN ELECTRICAL INSTALLATION BACKGROUND OF THE INVENTION 1.Field of the Invention This invention relates to electrical conductorsor electrical transmission lines which have good conductivecharacteristics for low frequency electrical phenomena, but whichpresent a resistance path for attenuating or damping high frequencyphenomena such as switching transients, travelling waves, and lightningsurges.

2. Description of Prior Art When a circuit breaker is closed to energizeor reclose a power line, voltage surges of relatively high magnitude andhigh frequency may be produced. This problem is particularly acuteduring the switching operation for energizing a capacitor bank whenprestriking causes travelling waves which are amplified at a cable linejunction and reflect at a transformer terminal and can causeend-of-the-line overvoltages of, for example, several times normal crestvoltage. High magnitude, high frequency voltage surges also occur on atransmission line when lightning strikes equipment connected to theline, or, in another example, during a short line fault.

The high frequency transients of the type which might occur on a highvoltage transmission line may have frequencies, for example, in therange 1 Kilohertz to l Megohertz (i.e., 1,000 cycles/sec. to 1,000,000cycles/sec.).

One well-known method of reducing the magnitude of switching surges isto preinsert a resistance of suitable value into the curcuit during theclosing operation just prior to the moment at which the main contactsengage. Other methods have involved the use of parallel surge-modifyingcapacitances in parallel with the transformer terminals; and a thirdprior art method of attenuating the undesirable high frequencyelectrical transients in a transmission line or the like has been theuse of series inductances in the line. The prior art methods justbriefly discussed are undesirable since they are costly, involve highlosses, and the resistor insertion method mentioned requires the use ofseparate switching means for the insertion of the resistor.

It is also known to utilize conductor arrangements for attenuatingundesirable high frequency transients which operate upon the principlethat high frequency currents tend to flow substantially only in theradially outer peripheral portion of the conductor due to the well-knownskin effect principle. Prior art teachings of high frequency transientattenuation which show utilization of the skin effect principle includeUS. Pat. Nos. 3,480,382 issued to Herman R. Person; 3,531,264 issued toHerman R. Person; 3,541,473 issued to Heinz M. Schlicke et al.; and3,543,105 issued to Robert I. Van Nice.

A literature reference relating to a utilization of the skin effectprinciple for attenuation of high frequency harmonics is provided in anarticle entitled High Frequency AC Harmonics on a HVDC Transmission LineMight Be Attenuated by Conductor Design" by John R. Abbott, published inthe periodical Transmission and Distribution," Aug. 1969, pp. 58-6inclusive.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide an improved electrical conductor arrangement which is a goodconductor for low frequencies such as 60 cycle electrical phenomena orfor direct currents but which presents a substantial resistance for highfrequency electrical phenomena such as switching transients andtraveling waves.

It is another object of the invention to provide for insertion in anelectrical conductor such as an electrical power transmission line ofother electrical installation a wave trap which attenuates or damps highfrequency electrical phenomena such as switching transients andtraveling waves but which presents a good conductive path for lowfrequency electrical phenomena such as 60 Hz (60 cycle) phenomena, andwhich wave trap is completely static, self-adjusting to transients andinexpensive to manufacture.

It is a further object of the invention to provide a wave trap assemblyfor insertion in series with a transmission line for attenuating ordamping high frequency electrical transients, but having good conductivecharacteristics for low frequency electrical phenomena, and whichassembly is compact and compatible with existing equipment.

In achievement of these objectives, there is provided in accordance withan embodiment of the invention a wave trap assembly for connection inseries with an electrical conductor means such as an electrical powertransmission line to attenuate or damp transient high frequencyphenomena, and comprising a non-magnetic conductor member received in aslot in a stack of magnetic laminations, whereby the inductive effect ofthe magnetic laminations causes displacement of the high frequencytransient currents into a reduced crosssectional area of the conductorcontinguous the outer periphery of the magnetic laminations, to modifythe action of the normal skin effect whereby to more effectivelyattenuate the high frequency phenomena. The conductor may be cast in theslot. In a modified embodiment, the radially or peripherally outerportion of the conductor lying in the slot of the stack of magneticlaminations may be made of a higher resistance material than theradially inner portion of the conductor. In a still further embodimentof a conductor lying in a slot in a stack of magnetic laminations, aradially inner conductor portion of larger cross section may beconnected by a narrow cross-section neck portion to a radially outerconductor portion of smaller cross section than the radially innerconductor portion whereby to promote the transfer of high frequencytransients to the outer conductor portion. In another embodiment, thewave trap assembly may comprise a plurality of circumferentialiy spacedconductor members lying in slots in the peripheral surface of adrum-like stack of magnetic laminations. In still another embodiment, aplurality of wave trap assemblies may be supported by stand-offinsulators and by conducting spacers in such manner as to be connectedin series with each other and in series with the power transmissionline.

Further objects and advantages of the invention will become apparentfrom the following description taken in conjunction with thefollowing'drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a wavetrap a sembly for attenuating high frequency transients in accordancewith the invention;

FIG. 2 is a cross-sectional view of the wave trap assembly of FIG. 1;

FIG. 2a is a graphical representation showing the high frequency currentdistribution in the conductor and the low frequency current distributionin the conductor relative to the height of the conductor;

FIG. 3 is a view in transverse cross-section of a modified conductoradapted for use in the wave trap assembly in place of the conductorshown in FIGS. 1 and 2, the conductor of FIG. 3 including a highresistance material contiguous the radially outer edge thereof;

FIG. 4 is a view of modified conductor which may be used in place of theconductor shown in FIGS. 1, 2 and 3, and including a small cross-sectionhigh resistance path for high frequency currents and a largercrosssection path for low frequency currents;

FIGS. 4a and 4b are views in transverse cross section of wave trapassemblies using conductors of triangular and square cross section,respectively;

FIG. 5 is a view in perspective of a modified wave trap assembly whichis generally similar to the wave trap assembly of FIG. 1 but in whichthe conductor member such as an aluminum or copper conductor(particularly aluminum) is cast in place in the slot in the magneticlaminations of the assembly;

FIG. 6 is a modified wave trap assembly along the lines of the structureshown in FIG. 5 in which the castin-place conductor includes integrallycast end portions which serve to retain the stack of magneticlaminations in assembled relation to each other;

FIG. 7 is a view in perspective of a modified wave trap assemblyincluding a plurality of parallelconnected conductor elements cast inplace in circumferentially spaced relation to each other around theperiphery of a drum-like structure formed of magnetic laminations;

FIG. 7a is a schematic diagram of a modified arrangement in which theconductors on drum 80 are connected in series with each other, ratherthan in parallel;

FIG. 8 is an enlarged view showing the cast-in-place conductor elementsof the embodiment of FIG. 7;

FIG. 9 is a view in vertical elevation of an assembly of a plurality ofwave trap" assemblies such as those shown in FIGS. 1-8, inclusive,connected in series with each other; and

FIG. 10 is a schematic illustration of a typical installation of wavetraps in series with an electrical transmission line.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1 thereis generally indicated at 10 a wave trap adapted to attenuate highfrequency electrical transients and adapted to be connected in serieswith an electrical transmission line. The wave trap 10 includes a stack12 of alternate disk-like circular laminations 14 of magnetic materialsuch as soft iron or transformer steel, and laminations 16 of a suitableelectrically insulating material. The insulating laminations 16 arenormally much thinner than the magnetic laminations 14, but the drawingsdo not attempt to show this. The function of insulating laminations 16is to prevent the ilow of electrical current through the magneticlaminations l4 lengthwise of the stack. Instead of using insulatinglaminations 16, as shown, the magnetic laminations 14 may instead becoated with an insulating varnish or the like to prevent the flow ofcurrent; or, as

a still further alternative, the normal oxides on the surface of themagnetic laminations may serve as an electrical insulating barrierbetween laminations which prevents the flow of current. It might benoted that upon the occurrence of high frequency electrical transients,the occurrence of eddy currents in the magnetic laminations is notundesirable, since the losses produced by such eddy currents arereflected as a resistance which tends to damp the high frequencytransients.

The stack 12 of the alternate magnetic and insulating laminations 14 and16 is provided with a radially extending slot 18 throughout the entirelength of the stack 12, and conductor member 20 of non-magnetic materialwhich is connected in series with the electrical transmission line isreceived within the slot 18. The conductor 20 is preferably sodimensioned that its height or radial dimension H relative to stack 12is substantially greater than its transverse or width dimension W. Inthe example shown in FIG. I, the conductor 20 is entirely of onematerial such as copper or aluminum, for example, having good electricalconductive characteristics. As can best be seen from an examination ofthe graph of FIG. 20, at ordinary low frequency power such as cycles,the current .is distributed substantially uniformly over the entireheight (H) of conductor 20 along the length of the conductor. However,if high frequency transient electrical currents which may, for example,beanywhere in the range 1 Kilohertz to l Megahertz (i.e., 1,000cycles/sec. l,000,000 cycles/- sec.), are flowing in the conductor 10 asmight be due to a switching operation or due to the occurrence of alightning surge, the high frequency transient currents flowsubstantially only in the radially outer portion of the height (H) ofconductor 20, near the circumference of the circular laminations 14, dueto the skin effect principle in accordance with which high frequencyelectrical currents move to the outer periphery of the electricalconductor, as modified by the fact that the conductor is received in theslot 18 of the stack of magnetic laminations 14.

If the conductor 20 were not received in the slot 18 of the magneticlaminations 14 as shown, the skin effect phenomena. would cause highfrequency currents to flow in a skin contiguous the entire periphery ofthe conductor (i.e., along all four edges of the conductor 20). However,when the conductor 20 is received in the slot 18, as shown, in FIG. 1,the inductive effect of the presence of the magnetic laminations 14 willcause the high frequency currents to flow only contiguous theperipherally (or radially) outer edge of conductor 20. The

. net effect of this is that the area of conductor 20 available forpassage of the high frequency transients is substantially less when theconductor 20 is received in the slot 18 of the stacked magneticlaminations, as shown in FIG. 1, than if the conductor 20 were not solocated. The skin effect phenomenon in effect reduces thecross-sectional area of the conductor which is available for carryingthe high frequency transient currents,

18 of stack 12 of magnetic laminations 14 as just described. As a resultof the foregoing, the high frequency electrical transient currents andvoltages are more greatly attenuated or damped due to the location ofconductor 20 in slot 18 of the magnetic laminations.

As shown in FIG. 3, the conductor generally indicated at 20' may be usedin substitution of the conductor 20 and be positioned in the slot 18shown in FIGS. 1 and 2. The conductor 20 of FIG. 3 is of generallyrectangular cross-section, preferably having a relatively largeheight-to-width ratio including a radially inner (relative to slot 18)conductor portion 22 which may be made of a non-magnetic material havinggood conductive properties such as copper or aluminum, and a radiallyouter conductor portion 24 which lies in radially abutting relation toconductor portion 22 and which is made of a higher resistancenon-magnetic material such as, for example, l lead; (2) tin; (3)aluminum (if conductor 22 is made of copper); (4) fibre metal made ofanon-magnetic metal; or (5) foam metal made ofa non-magnetic meta]. Allof the materials just mentioned have a higher resistance per unit lengththan does the conductive material such as copper of which the portion 22of the conductor is made. Low power frequencies will flow mostly ininner conductor portion 22. High frequency transients will, due to skineffect as enhanced by the location of conductor 20' in the slot 18 inthe stack of magnetic laminations, flow substantially exclusively in theouter conductor portion 24 where the high resistance material, togetherwith the reduced cross sectional area of conductor portion 24 ascompared to the substantially larger cross-sectional area of theconductor portion 22, will substantially attenuate the high frequencytransients flowing through high resistance conductor portion 24.

For a given material of which radially outer portion 24 of conductor 20is made, a given frequency of the high frequency transients will flow ata certain depth radially inwardly of the outer periphery of theconductor portion 24. This depth will vary for a given material of whichportion 24 is made depending upon the frequency of the transients, thedepth of the skin in which the current flows decreasing with increase infrequency. In determining the radial depth of high resistance conductorportion 24, allowance should be made for the low end of the range oftransient frequencies which it is desired to attenuate.

Referring now to FIG. 4 there is shown a further modification in which anon-magnetic conductor generally indicated at 30 is a composite memberincluding a radially inner portion of larger cross-section 32 and aradially outer portion 34 of small cross-section compared to thecross-section 32. The radially inner and outer portions 32 and 34 of theconductor 30 are connected by a connecting narrow conducting neckportion 36 of non-magnetic material. The composite conductor 30 (formedof portions 32-34-36) is received in a correspondingly-shaped slot in anassembly generally indicated at 40 which may be similar to the stack 12shown in FIG. 1 and be composed ofa plurality of alternately arrangedmagnetic laminations and laminations of insulating material suitablyheld together in stacked relation to each other. The slot extends forthe entire axial length of assembly 40. Instead of using insulatinglaminations, the magnetic laminations may be coated with an insulatingcoating to prevent flow of electrical current along the stack oflaminations as previously explained. The radially outer conductorportion 34 may include a narrow projecting neck portion 37 which extendsto the outer periphery of assembly 40. Alternatively, the space occupiedby projecting neck portion 37 may be left as an air gap. The narrowconnecting neck portion 36 may also be left as an air gap for most ofthe length of the wave trap, the conductor portions 32 and 34 beingconductively connected together at each end of the wave trap, thusplacing conductor portions 32 and 34 in electrically parallel relationwith each other.

The portion 32 of composite conductor 30 in FIG. 4 carries the lowfrequency currents, such as cycles, (60 Hz) but upon the occurrence ofhigh frequency transient currents, such as during a switching operationor a lightning surge, the high frequency transient cur rents, due to theskin effect principle, and enhanced by the location of the conductor 30in the stack of magnetic laminations, move to the outer peripheralportion 34 of the composite conductor. The reduced crosssectional areaof the conductor portion 34, provides a substantially increasedresistance per unit length as compared to the resistance of the largercross-sectional area inner conductor portion 32, with the result thatthe higher resistance of the conductor portion 34 causes substantialattenuation of the high frequency electrical transients flowing throughthe portion 34 of the composite conductor 30.

The narrow slot 36 connecting radially inner and outer conductorportions 32 and 34 due to its narrowness provides a gap of decreaseddimensions in the magnetic laminations of stack 40, thus increasing themagnetic permeability of the magnetic flux path around lower conductorportion 32, thereby increasing the inductance of lower conductor portion32. As previously explained, slot 36' receives conductor portion 36 ofnon-magnetic material, preferably the same material as conductorportions 32 and 34.

The increased inductance of lower conductor portion 32 due to thenarrowness of slot 36' promotes the shifting of the higher frequencycurrents (when these occur) into the smaller cross-section radiallyouter conductor portion 34, where the increased resistance to highfrequency current flow due to the smaller crosssection of conductorportion 34 causes the attenuation of high frequency currents andvoltages.

The composite conductor 34] may be made of one non-magnetic metal ofgood electrical conductive properties such as copper or aluminum, themetal being cast into the slot in the stack of laminations by a diecasting process.

There is shown in FIG. 4a a stack 41 of magnetic laminations suitableinsulated from each other similar to the stacks previously described,and provided contiguous the outer periphery of the stack with a slot oftriangular cross-section in which a conductor generally indicated at 42of a metal such as copper or aluminum is positioned. The apex 43 of thetriangular crosssection conductor is positioned at the radially outerportion of the conductor and base 44 of conductor 42 lies at theradially inner portion of the conductor. When power frequency currentssuch as 60 cycle currents are passing through conductor 42, the currentwill be distributed substantially uniformly over the crosssection ofconductor 42. However, upon the occurrence of high frequency transientcurrents, such currents, due to skin effect, as enhanced by the locationof the conductor 42 in the stack of magnetic laminations, will tend tocrowd into a relatively small cross-section area of the conductor in aregion near apex 43,

whereby to provide increased resistance to flow of the high frequencytransient currents.

There is shown in FIG. 4b a stack 45 of magnetic laminations similar tothose previously described, and having a slot in which a conductor 47 ofsquare crosssection is positioned. As previously described, highfrequency currents will crowd into the radially outer portion of theconductor, whereby the reduced crosssectional area available for thehigh frequency transients will increase the resistance to the flow ofhigh frequency transients thereby attenuating or damping the highfrequency transients.

Referring now to FIG. there is shown a modified wave trap construction,generally indicated at 50, for connection in series with a powertransmission line and including a stack 51 of rectangular laminations 52of steel or of other suitable magnetic material with insulatinglaminations or other suitable insulation 53 between adjacent magneticlaminations. The stack 51 of laminations 52 and 53 is provided with aslot 54 extending for the entire length thereof; and an aluminum orcopper conductor generally indicated at 56 is cast in the slot 54.Aluminum is preferably used as the conductor metal when the conductoriscast in the slot. The metal conductor 56 includes end portions thereofindicated at 58 which extend beyond the opposite ends of the stack 51.The operation of the embodiment of FIG. 5 is similar to the embodimentof FIG. 1 previously described.

Referring now to FIG. 6 there is shown a still further modified wavetrap assembly generally indicated at 60 which is generally similar tothe wave trap assembly shown in FIG. 5 and includes a stack 61 ofrectangular laminations of magnetic material such as iron or steelindicated at 62 with contiguous magnetic laminations being separated byinsulating spacers or laminations or other suitable insulation 63. Theassembly or stack 61 is provided throughout its length with alongitudinally extending slot 64 similar to the slot shown in FIGS. 1, 2and 5 and a conductor member 65 of a suitable nonmagnetic conductivematerial such as aluminum is cast into the slot 64. However, in the caseof the embodiment of FIG. 6, the cast material is cast in such manner asto include end portions 68 at the opposite ends of stack 61, which endportions 68 constitute end clamping members for the stack 61 of magneticand insulating laminations. Conductor lug portions 70 integrally castwith the end portions 68 and with the main conductor 65 extendlongitudinally beyond the end portions 68 for connection into theelectrical power transmission circuit. The operation of the embodimentof FIG. 6 is similar to the operation of the embodiment of FIG. 1previously described.

Referring now to FIGS. 7 and 8 there is shown a still further modifiedform of the invention including a cylindrical drum-like member generallyindicated at 80 formed of a plurality of stacked laminations 82 ofmagnetic material such as iron or steel alternated with laminations 83of insulating material. Instead of using insulating laminations 83, themagnetic laminations 82 may instead be coated with an insulationmaterial. The laminations 82 and 83 are of circular shape. Each of thecircular-shaped laminations 82 and 83 is provided at its periphery witha plurality of circumferentially spaced radially inwardly extendingslots 84, each communicating a short distance radially inwardly from theouter periphery of the laminations 82 or 83 with a circularcross-section slot portion 86. When the plurality of laminations 82 and83 are stacked in assembled relation to each other, they together definea plurality of radially and axially extending slot portions 84' ofrectangular cross-section each communicating at the radially inner endthereof with a generally circular shaped cross-section radially andaxially extending slot portion 86' to define a plurality of compositeslots (composite of slot portions 84' and 86') each generally indicatedat 87 extending for the axial length of the stack assembly. Suitablemeans, not shown, are provided for holding the stack of laminations inaxially assembled stacked relation. Conductor elements 91 of nonmagneticmaterial such as aluminum are cast into each of the plurality ofcomposite slots 87 for the entire axial length of the stack 80. Suitableconductor means such as conducting end plate 89 and a connection stud 90conductively connected to end plate 89 are provided at each of theopposite axial ends of the assembly 80 for connecting the castconductors in the plurality of composite slots 87 in parallel relationto each other. The assembly shown in FIG. 7 is connected in series withthe transmission line by means of the connection stud 90 at each end ofdrum 80. The connection studs 90 are only located at the opposite endsof the assembly shown in FIG. 7 and do not extend through the assembly.

When the current flow through the transmission line is of normal powerfrequency such as 60 cycles per second (60 Hz), the current will flowthrough the conductor portions 86A in the radially inner larger diameterportions 86' of the slots. However, upon the occurrence of highfrequency transient currents in the transmission line, the skin effectprinciple will cause the high frequency currents to flow in theconductor portions 84A lying in the radially outer reducedcross-sectional area slot portions 84'. Because of their reducedcrosssectional area, the reduced cross-sectional area conductor portions84A lying in slot portions 84' have a higher resistance than the largercross-section conductor portions 86A, lying in the slot portions 86' tothereby cause attenuation of the high frequency electrical transientsflowing in the reduced cross-sectional area conductor portions 84A.

The conductors carried by the drum-like member 80 shown in FIG. 7 mayassume other forms, as for example, the forms shown in FIGS. 1, 3, 4, 4aand 4b. Also, while the plurality of conductors carried by drum 80 havebeen shown and described as being connected in parallel with each other,it may instead be desirable as schematically shown in FIG. 7a, toconnect the plurality of conductors 91' in series with each other by theuse of suitable cross-over end connections 93 and with proper insulationof the conductors 91' from the stack of laminations (required in thecase of a series connection of the conductors), as would be obvious toone skilled in the art. The opposite ends of the series winding of FIG.7a are connected to terminals 90'.

Referring now to FIG. 9, there'is diagrammatically shown an assembly ofa plurality of wave traps connected in series relation with each otherand in series with a transmission line. The assembly of FIG. 9 isgenerally indicated at 100. The assembly includes a supporting metalframe 102 which is mounted on a suitable centrally located stand-offinsulator or insulators 104 which, in turn, are supported at the lowerend thereof upon a suitable support 106. The assembly shown at 100includes a pair of subassemblies respectively generally indicated at108A and 1088. Each of the subassemblies 108A and 1088 includes aplurality of separate wave traps indicated at 110, 112, and 114 insubassembly 108A and at 116, 118 and 120 in subassembly 1088. Each ofthe wave traps diagrammatically indicated at 110, 112, 114, 116, 118,and 120 may be similar to any one of the wave traps shown in any of theprevious embodiments. The wave trap 110 is supported upon a pair ofstand-off insulators or insulating posts 122 and 124 which, in turn, aresupported by metal frame member 102. The wave trap 112 is supported atthe left-hand end thereof relative to the view of FIG. 9 by aninsulating post 126 suitably supported on insulating post 122, and atthe right-hand end thereof relative to the view of FIG. 9 by aconductive structural member or conductive spacer 128 suitably supportedon insulating post 124.

As viewed in FIG. 9, the wave trap 114 is supported at the left-hand endthereof by a conductive structural member or spacer 130 supported byinsulator post 126, wave trap 114 being supported at the right-hand endthereof by an insulator post 132 mounted on conductive spacer 128.

Each of the stand-off insulators such as 122, 124, and each of theconductive spacers such as 128 is provided at each end thereof with aflanged sleeve such as those indicated at 125 which is bolted to thecontiguous vertically aligned stand-off insulator or spacer, as the casemay be, and is also bolted to the projecting conductor member such as127 of a wave trap, whereby to hold the stand-off insulators, conductingspacer, and wave trap assemblies in assembled relation to each other, asseen in FIG. 9.

In the subassembly 1088 of FIG. 9, the wave trap 116 is supported at theopposite ends thereof by insulator posts 134 and 136 mounted on framemember 102. The wave trap 118 is mounted above the wave trap 116 and issupported at the left-hand end thereof by the conductive structuralmember or spacer 138 mounted on insulator post 134 and wave trap 118 issupported at the opposite or right-hand end thereof by the insulatorpost 140 mounted on insulator post 136. The wave trap 120 is supportedabove the wave trap 118 at the left-hand end thereof, relative to theview of FIG. 9, by an insulator post 142 mounted on conductivestructural member 138 and is supported at the right-hand end thereof bya conductive spacer or structural member 144 mounted on insulator post140.

The total assembly 100 including the two subassemblies 108A and 1088 isconnected in series with the transmission line by a connection atterminal 146 of the wave trap 110 and by a terminal 148 at theright-hand end of the wave trap 116, relative to the view of FIG. 9. Thetwo subassemblies 108A and 1088 are connected in series with each otherby conductor member 150 between one end of wave trap 114 and thecontiguous end of the wave trap 120. It can thus be seen that by meansof the conductive members 146, 128, 130, 150, 144, 138 and 148, theplurality of wave traps 110, N2, 114, 116, 118 and 120 are connected inseries with each other and with the transmission line. A conductive tapmember 152 is connected to the conductor member 150 between the two wavetrap subassemblies 108A and 10813 to permit one-half of the totalassembly to be connected in the circuit of the transmission line ifdesired.

Refer now to FIG. 10 which schematically shows a typical installation ofwave traps in accordance with the invention in series with an electricaltransmission line. There is shown a generating station generallyindicated at 200, including an alternating current generator 202 havingits output connected to the transmission line 204 through a step-uptransformer 206, a first wave trap 208, and a circuit breaker 210. Atthe generating station end, preferably another wave trap 211 isinterposed between circuit breaker 210 and transmission line 204. Notethat the first wave trap 208 is interposed between the step-uptransformer 206 and the circuit breaker 210 and the second wave trap 211is interposed between circuit breaker 210 and transmission line 204.

The opposite end of the transmission line 204, which may be miles long,for example, is connected to a load 214 at a load station generallyindicated 212 through a circuit breaker 216, a wave trap 218, and astep-down transformer 220. Note that the wave trap 218 is interposedbetween the circuit breaker 216 and the step-down transformer 220. Thewave traps 208, 21 l, and 218 diagramatically shown in FIG. 10 may be ofany of the types hereinbefore described and each may respectivelyinclude a plurality of wave traps, as dictated by the requirements ofthe installation.

While the wave trap assemblies have been described hereinbefore for usein connection with a conductor or transmission line which normallycarries alternating current, any of the wave trap assemblies of theinvention may also be inserted in series with a conductor which carriesdirect current, such as, for example, a high voltage direct current(l-IVDC) transmission line of the type described in the aforementionedarticle by John R. Abbott, published in the periodical Transmission andDistribution, Aug. 1969, pages 58-60, inclusive, in which case the wavetrap or wave traps would damp or attenuate high frequency transientssuch as the alternating current harmonics or ripple present on thedirect current transmission line.

From the foregoing detailed description of the invention, it has beenshown how the objects of the invention have been obtained in a preferredmanner. However, modifications and equivalents of the disclosed conceptssuch as readily occur to those skilled in the art are intended to beincluded within the scope of this invention.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents in said circuit, but which transmits electrical voltages andcurrents of normal power frequency or direct current without substantialattenuation thereof, comprising a body of magnetic material, a slotextending inwardly and lengthwise of said body from an outer peripheralsurface of said body, and an electrical conductor member of non-magneticmaterial received in said slot in magnetically inductive relation tosaid magnetic body, said conductor member extending to contiguous theouter peripheral end of said slot, said conductor member havingsubstantially greater electrical conductivity than said magneticmaterial, said conductor member being adapted to be connected in circuitwith said conductor means whereby to transmit through said conductormember without substantial attenuation electrical currents of normalpower frequency and direct current but with substantial attentuation ofhigh frequency electrical voltages and currents.

2. An apparatus as defined in claim 1 in which said conductor member isof triangular cross section, with an apex of the triangular crosssection being located at a peripherally outer portion of said slot,whereby to provide a reduced cross-sectional area and hence higherresistance path in the. region of said apex for flow of high frequencycurrents.

3. An apparatus as defined in claim 1 which said conductor means is anelectrical transmission line.

4. An apparatus as defined in claim 1 in which said conductor member isa casting in said slot.

5. An apparatus as defined in claim 4 including end clamping means ateach of the opposite ends of said stack, and lug-like conductor meansconductively connected to said end clamping means, said end clampingmeans, said lug-like conductor means, and the conductor member in saidslot all being a unitary casting.

6. An apparatus defined in claim 1 in which said body of magneticmaterial is provided with a plurality of slots each extending lengthwiseof said body and each extending inwardly from an outer peripheral edgeof said body, said slots being spaced from each other peripherally ofsaid body, and conductor means positioned in each of said slots.

7. An apparatus as defined in claim 6 in which said body of magneticmaterial is in the form of a cylindrical drum.

8. An apparatus as defined in claim 6 in which the conductor meanspositioned in the plurality of slots are connected in parallel with eachother and in series with the transmission line.

9. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a body of magnetic material, a slot extendinginwardly and lengthwise of said body from an outer peripheral edge ofsaid body, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic material, said conductor member being adapted to be connectedin circuit with said conductor means, said conductor member including afirst portion lying in an inner portion of said slot in inwardly spacedrelation to the outer periphery of said slot and made of material havinggood electrical conductive properties, and a second portion lying insaid slot outwardly of said first portion and nearer the outer peripheryof said slot, said second portion being made of a material which is notas good an electrical conductor as the material of said first portion,whereby said second portion serves as a higher resistance conductivepath for high frequency currents.

10. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a body of magnetic material, a slot extendinginwardly and lengthwise of said body from an outer peripheral edge ofsaid body, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic material, said conductor member being adapted to be connectedin circuit with said conductor means, said conductor member including afirst portion lying in an inner portion of said slot in inwardly spacedrelation to the outer periphery of said slot and a second portion lyingin said slot outwardly of said first portion and nearer the outerperiphery of said slot, said first portion being of substantiallygreater cross-sectional area than said second portion, whereby thesmaller cross-sectional area of said second portion presents anincreased resistance to high frequency currents flowing in said secondportion.

11. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a body of magnetic material, said body of magneticmaterial being provided with a plurality of slots each extendinglengthwise of said stack and each extending inwardly from an outerperipheral edge of said body, said slots being spaced from each otherperipherally of said body, a conductor member of non-magnetic materialpositioned in each of said slots in magnetically inductive relation tosaid magnetic material and adapted to be connected in circuit with saidconductor means, each conductor member including a first portion lyingin an inner portion of the respective slot in inwardly spaced relationto the outer periphery of said slot, and a second portion lying in therespective slot outwardly of said first portion and nearer the outerperiphery of said slot, said first portion being of substantiallygreater cross-sectional area than said second portion, whereby thesmaller cross-sectional area of said second portion presents anincreased resistance to high frequency currents flowing in said secondportion.

12. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a body of magnetic material, said body of magneticmaterial being provided with a plurality of slots each extendinglengthwise of said body and each extending inwardly from an outerperipheral edge of said body, said slots being spaced from each otherperipherally of said body, and an electrical conductor member ofnon-magnetic material positioned in each of said slots in magneticallyinductive relation to said magnetic material, the conductor memberspositioned in the plurality of slots being connected in series with eachother and in circuit with the electrical conductor means.

13. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a body of magnetic material, a slot extendinginwardly and lengthwise of said body from an outer peripheral edge ofsaid body, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic material, said conductor member being adapted to be connectedin circuit with said conductor means, said conductor member including afirst portion lying in an inner portion of said slot in inwardly spacedrelation to the outer periphery of said slot and a second portion lyingin said slot outwardly of said first portion and nearer the outerperiphery of said slot, said first portion being of substantiallygreater cross-sectional area than said second portion, whereby thesmaller cross-sectional area of said second portion presents anincreased resistance to high frequency currents flowing in said secondportion, and a narrow neck-like conductor portion connecting said firstportion and said second portion along substantially the entire length ofsaid first and said second portions.

14. An apparatus for connection in circuit with an electrical conductormenas to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a body of magnetic material, a slot extendinginwardly and lengthwise of said stack from an outer peripheral edge ofsaid body, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic material, said conductor member being connected in circuit withsaid conductor means, said conductor member including a first portionlying in an inner portion of said slot in inwardly spaced relation tothe outer periphery of said slot and a second portion lying in said slotoutwardly of said first portion and nearer the outer periphery of saidslot, said first portion being of substantially greater cross-sectionalarea than said second portion, whereby the smaller cross-sectional areaof said second portion presents an increased resistance to highfrequency currents flowing in said second portion, said first portionand said second portion being separated by an air gap along asubstantial part of the length of said first portion and said secondportion, corresponding ends of said first portion and said secondportion being conductively connected to each other.

15. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a stack of magnetic laminations, a slot extendinginwardly and lengthwise of said stack from an outer peripheral edge ofsaid stack, and an electrical conductor member of nonmagnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic laminations, said conductor member being adapted to beconnected in circuit with said conductor means, said conductor memberincluding a first portion lying in an inner portion of said slot ininwardly spaced relation to the outer periphery of said slot and made ofmaterial having good electrical conductive properties, and a secondportion lying in said slot outwardly of said first portion and nearerthe outer periphery of said slot, said second portion being made of amaterial which is not as good an electrical conductor as the material ofsaid first portion, whereby said second portion serves as a higherresistance conductive path for high frequency currents.

16. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a stack of magnetic laminations, a slot extendinginwardly and lengthwise of said stack from an outer peripheral edge ofsaid stack, and an electrical conductor member of nonmagnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic laminations, said conductor member being adapted to beconnected in circuit with said conductor means, said conductor memberincluding a first portion lying in an inner portion of said slot ininwardly spaced relation to the outer periphery of said slot and asecond portion lying in said slot outwardly of said first portion andnearer the outer periphery of said slot, said first portion being ofsubstantially greater cross-sectional area then said second portion,whereby the smaller cross-sectional area of said second portion presentsan increased resistance to high frequency currents flowing in saidsecond portion.

17. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents in said circuit but which transmits electrical voltages andcurrents of normal power frequency or direct current without substantialattenuation thereof, comprising a stack of magnetic laminations, saidstack of magnetic laminations being provided with a plurality of slotseach extending lengthwise of said stack and each extending inwardly froman outer peripheral edge of said stack, said slots being spaced fromeach other peripherally of said stack, a conductor member ofnon-magnetic material positioned in each of said slots in magneticallyinductive relation to said magnetic laminations and adapted to beconnected in circuit with said conductor means, each conductor memberincluding a first portion lying in an inner portion of the respectiveslot in inwardly spaced relation to the outer periphery of said slot,and a second portion lying in the respective slot outwardly of saidfirst portion and nearer the outer periphery of said slot, said firstportion being of substantially greater cross-sectional area than saidsecond portion, whereby the smaller cross-sectional area of said secondportion presents an increased resistance to high frequency currentsflowing in said second portion.

18. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a stack of magnetic laminations, said stack ofmagnetic laminations being provided with a plurality of slots eachextending lengthwise of said stack and each extending inwardly from anouter peripheral edge of said stack, said slots being spaced from eachother peripherally of said stack, and an electrical conductor member ofnon-magnetic material positioned in each of said slots in magneticallyinductive relation to said magnetic laminations, the conductor memberspositioned in the plurality of slots being connected in series with eachother and in circuit with the electrical conductor means.

19. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a stack of magnetic laminations, a slot extendinginwardly and lengthwise of said stack from an outer peripheral edge ofsaid stack, and an electrical conductor member of nonmagnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic laminations, said conductor member being adapted to beconnected in circuit with said conductor means, said conductor memberincluding a first portion lying in an inner portion of said slot ininwardly spaced relation to the outer periphery of said slot and asecond portion lying in said slot outwardly of said first portion andnearer the outer periphery of said slot, said first portion being ofsubstantially greater cross-sectional area than said second portion,whereby the smaller cross-sectional area of said second portion presentsan increased resistance to high frequency currents flowing in saidsecond portion, and a narrow neck-like conductor portion connecting saidfirst portion and said second portion along substantially the entirelength of said first and said second portions.

20. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a stack of magnetic laminations, a slot extendinginwardly and lengthwise of said stack from an outer peripheral edge ofsaid stack, and an electrical conductor member of nonmagnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic laminations, said conductor member being connected in circuitwith said conductor means, said conductor member including a firstportion lying in an inner portion of said slot in inwardly spacedrelation to the outer periphery of said slot and a second portion lyingin said slot outwardly of said first portion and nearer the outerperiphery of said slot, said first portion being of substantiallygreater cross-sectional area than said second portion, whereby thesmaller cross-sectional area of said second portion presents anincreased resistance to high frequency currents flowing in said secondportion, said first portion and said second portion being separated byan air gap along a substantial part of the length of said firstportion-and said second portion, corresponding ends of said firstportion and said second portion being conductively connected to eachother.

21. An assembly of damping devices for attenuating high frequencytransient phenomena for connection in circuit with an electricaltransmission line, each damping device comprising an electricalconductor member extending lengthwise thereof, said assembly comprisinga supporting frame member, stand-off insulator means supporting andspacing said frame member relative to a supporting surface, first andsecond stand-off insulator members positioned in longitudinally spacedrelation to each other along said frame member, a first damping devicesupported contiguous the respective opposite ends thereof by said firstand said second stand-off insulator members, means adapted toconductively connect one end of said first damping device in series withsaid electrical transmission line, said one end of said first dampingdevice being supported by said first stand-off insulator member, a firstconductive spacer member, said first conductive spacer member beingsupported on and substantially in axial alignment with said secondstand-off insulator member, a third stand-off insulator member supportedon and substantially in axial alignment of the said first stand-offinsulator member, a second damping device supported at one end thereofby said third stand-off insulator member and at the opposite end thereofby said first conductive spacer member, the end of said first dampingdevice opposite said one end of said first damping device beingconductively connected to said opposite end of said second dampingdevice through said first conductive spacer member, whereby to placesaid first and said second damping devices electrically in series witheach other, and means adapted to connect said one end of said seconddamping device in circuit with said electrical transmission line,whereby said first and said second damping devices are connected inseries with each other and are adapted to be connected in circuit withthe electrical transmission line.

22. An assembly of damping devices as defined in claim 21 in which saidmeans adapted to connect said one end of said second damping device incircuit with said electrical transmission line comprises additionaldamping devices connected in series with said second damping device, thelast of said additional damping devices being adapted to be connected tothe transmission line, whereby to place said assembly in circuit withthe transmission line.

23. An assembly of damping devices as defined in claim 21 in which therespective damping devices are of the type comprising a stack ofmagnetic laminations and a corresponding conductor member received in aslot in each respecitve stack, the conductor members of the plurality ofdamping devices being connected in series with each other and in circuitwith the transmission line.

24. An assembly of damping devices for attenuating high frequencytransient phenomena for connection in circuit with an electricaltransmission line, said assembly comprising a supporting frame member,stand-off insulator means supporting and spacing said frame memberrelative to a supporting surface, and a stack of damping devicessupported on said frame member in a plane substantially normal to saidsupporting surface, said stack comprising first and second stand-offinsulator members positioned in longitudinally spaced relation to eachother along said frame member, a first damping device supported inspaced relation to said frame member by said first and second stand-offinsulator members, means adapted to conductively connect one end of saidfirst damping device in circuit with the electrical transmission line,said stack comprising a plurality of additional damping devices eachsupported in said plane in stacked relation to said first damping deviceand to each other by a corresponding additional stand-off insulator atone end of each respective damping device and by a correspondingconductive spacer at an opposite end of each respective clamping device,the relative position of the corresponding stand-off insulator and ofthe corresponding conductive spacer being reversed for successivedamping devices in the said stack whereby each corresponding conductivespacer establishes a conductive connection between successive dampingdevices to place successive damping devices electrically in series witheach other, and whereby to place the plurality of damping devices of thestack in series with each other, and means adapted to conelectricaltransmission line comprises at least one additional stack of dampingdevices as defined in claim 18 whereby to place said at least oneadditional stack of damping devices in series with said first-mentionedstack and in circuit with said transmission line.

1. An apparatus for connection in circuit with an electrical conductormeans to substantially attenuate high frequency electrical voltages andcurrents in said circuit, but which transmits electrical voltages andcurrents of normal power frequency or direct current without substantialattenuation thereof, comprising a body of magnetic material, a slotextending inwardly and lengthwise of said body from an outer peripheralsurface of said body, and an electrical conductor member of nonmagneticmaterial received in said slot in magnetically inductive relation tosaid magnetic body, said conductor member extending to contiguous theouter peripheral end of said slot, said conductor member havingsubstantially greater electrical conductivity than said magneticmaterial, said conductor member being adapted to be connected in circuitwith said conductor means whereby to transmit through said conductormember without substantial attenuation electrical currents of normalpower frequency and direct current but with substantial attentuation ofhigh frequency electrical voltages and currents.
 2. An apparatus asdefined in claim 1 in which said conductor member is of triangular crosssection, with an apex of the triangular cross section being located at aperipherally outer portion of said slot, whereby to provide a reducedcrosssectional area and hence higher resistance path in the region ofsaid apex for flow of high frequency currents.
 3. An apparatus asdefined in claim 1 which said conductor means is an electricaltransmission line.
 4. An apparatus as defined in claim 1 in which saidconductor member is a casting in said slot.
 5. An apparatus as definedin claim 4 including end clamping means at each of the opposite ends ofsaid stack, and lug-like conductor means conductively connected to saidend clamping means, said end clamping means, said lug-like conductormeans, and the conductor member in said slot all being a unitarycasting.
 6. An apparatus defined in claim 1 in which said body ofmagnetic material is provided with a plurality of slots each extendinglengthwise of said body and each extending inwardly from an outerperipheral edge of said body, said slots being spaced from each otherperipherally of said body, and conductor means positioned in each ofsaid slots.
 7. An apparatus as defined in claim 6 in which said body ofmagnetic material is in the form of a cylindrical drum.
 8. An apparatusas defined in claim 6 in which the conductor means positioned in theplurality of slots are connected in parallel with each other and inseries with the transmission line.
 9. An apparatus for connection incircuit with an electrical conductor means to substantially attenuatehigh frequency electrical voltages and currents but which transmitselectrical voltages and currents of normal power frequency or directcurrent without substantial attenuation thereof, comprising a body ofmagnetic material, a slot extending inwardly and lengthwise of said bodyfrom an outer peripheral edge of said body, and an electrical conductormember of non-magnetic material received in said slot in magneticallyinductive relation to said magnetic material, said conductor memberbeing adapted to be connected in circuit with said conductor means, saidconductor meMber including a first portion lying in an inner portion ofsaid slot in inwardly spaced relation to the outer periphery of saidslot and made of material having good electrical conductive properties,and a second portion lying in said slot outwardly of said first portionand nearer the outer periphery of said slot, said second portion beingmade of a material which is not as good an electrical conductor as thematerial of said first portion, whereby said second portion serves as ahigher resistance conductive path for high frequency currents.
 10. Anapparatus for connection in circuit with an electrical conductor meansto substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a body of magnetic material, a slot extendinginwardly and lengthwise of said body from an outer peripheral edge ofsaid body, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic material, said conductor member being adapted to be connectedin circuit with said conductor means, said conductor member including afirst portion lying in an inner portion of said slot in inwardly spacedrelation to the outer periphery of said slot and a second portion lyingin said slot outwardly of said first portion and nearer the outerperiphery of said slot, said first portion being of substantiallygreater cross-sectional area than said second portion, whereby thesmaller cross-sectional area of said second portion presents anincreased resistance to high frequency currents flowing in said secondportion.
 11. An apparatus for connection in circuit with an electricalconductor means to substantially attenuate high frequency electricalvoltages and currents but which transmits electrical voltages andcurrents of normal power frequency or direct current without substantialattenuation thereof, comprising a body of magnetic material, said bodyof magnetic material being provided with a plurality of slots eachextending lengthwise of said stack and each extending inwardly from anouter peripheral edge of said body, said slots being spaced from eachother peripherally of said body, a conductor member of non-magneticmaterial positioned in each of said slots in magnetically inductiverelation to said magnetic material and adapted to be connected incircuit with said conductor means, each conductor member including afirst portion lying in an inner portion of the respective slot ininwardly spaced relation to the outer periphery of said slot, and asecond portion lying in the respective slot outwardly of said firstportion and nearer the outer periphery of said slot, said first portionbeing of substantially greater cross-sectional area than said secondportion, whereby the smaller cross-sectional area of said second portionpresents an increased resistance to high frequency currents flowing insaid second portion.
 12. An apparatus for connection in circuit with anelectrical conductor means to substantially attenuate high frequencyelectrical voltages and currents but which transmits electrical voltagesand currents of normal power frequency or direct current withoutsubstantial attenuation thereof, comprising a body of magnetic material,said body of magnetic material being provided with a plurality of slotseach extending lengthwise of said body and each extending inwardly froman outer peripheral edge of said body, said slots being spaced from eachother peripherally of said body, and an electrical conductor member ofnon-magnetic material positioned in each of said slots in magneticallyinductive relation to said magnetic material, the conductor memberspositioned in the plurality of slots being connected in series with eachother and in circuit with the electrical conductor means.
 13. Anapparatus for connection in circuit with an electrical conductor meansto substAntially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a body of magnetic material, a slot extendinginwardly and lengthwise of said body from an outer peripheral edge ofsaid body, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic material, said conductor member being adapted to be connectedin circuit with said conductor means, said conductor member including afirst portion lying in an inner portion of said slot in inwardly spacedrelation to the outer periphery of said slot and a second portion lyingin said slot outwardly of said first portion and nearer the outerperiphery of said slot, said first portion being of substantiallygreater cross-sectional area than said second portion, whereby thesmaller cross-sectional area of said second portion presents anincreased resistance to high frequency currents flowing in said secondportion, and a narrow neck-like conductor portion connecting said firstportion and said second portion along substantially the entire length ofsaid first and said second portions.
 14. An apparatus for connection incircuit with an electrical conductor menas to substantially attenuatehigh frequency electrical voltages and currents but which transmitselectrical voltages and currents of normal power frequency or directcurrent without substantial attenuation thereof, comprising a body ofmagnetic material, a slot extending inwardly and lengthwise of saidstack from an outer peripheral edge of said body, and an electricalconductor member of non-magnetic material received in said slot inmagnetically inductive relation to said magnetic material, saidconductor member being connected in circuit with said conductor means,said conductor member including a first portion lying in an innerportion of said slot in inwardly spaced relation to the outer peripheryof said slot and a second portion lying in said slot outwardly of saidfirst portion and nearer the outer periphery of said slot, said firstportion being of substantially greater cross-sectional area than saidsecond portion, whereby the smaller cross-sectional area of said secondportion presents an increased resistance to high frequency currentsflowing in said second portion, said first portion and said secondportion being separated by an air gap along a substantial part of thelength of said first portion and said second portion, corresponding endsof said first portion and said second portion being conductivelyconnected to each other.
 15. An apparatus for connection in circuit withan electrical conductor means to substantially attenuate high frequencyelectrical voltages and currents but which transmits electrical voltagesand currents of normal power frequency or direct current withoutsubstantial attenuation thereof, comprising a stack of magneticlaminations, a slot extending inwardly and lengthwise of said stack froman outer peripheral edge of said stack, and an electrical conductormember of non-magnetic material received in said slot in magneticallyinductive relation to said magnetic laminations, said conductor memberbeing adapted to be connected in circuit with said conductor means, saidconductor member including a first portion lying in an inner portion ofsaid slot in inwardly spaced relation to the outer periphery of saidslot and made of material having good electrical conductive properties,and a second portion lying in said slot outwardly of said first portionand nearer the outer periphery of said slot, said second portion beingmade of a material which is not as good an electrical conductor as thematerial of said first portion, whereby said second portion serves as ahigher resistance conductive path for high frequency currents.
 16. Anapparatus for connection in circuit with an electrical conductor meansto substantiaLly attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a stack of magnetic laminations, a slot extendinginwardly and lengthwise of said stack from an outer peripheral edge ofsaid stack, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic laminations, said conductor member being adapted to beconnected in circuit with said conductor means, said conductor memberincluding a first portion lying in an inner portion of said slot ininwardly spaced relation to the outer periphery of said slot and asecond portion lying in said slot outwardly of said first portion andnearer the outer periphery of said slot, said first portion being ofsubstantially greater cross-sectional area then said second portion,whereby the smaller cross-sectional area of said second portion presentsan increased resistance to high frequency currents flowing in saidsecond portion.
 17. An apparatus for connection in circuit with anelectrical conductor means to substantially attenuate high frequencyelectrical voltages and currents in said circuit but which transmitselectrical voltages and currents of normal power frequency or directcurrent without substantial attenuation thereof, comprising a stack ofmagnetic laminations, said stack of magnetic laminations being providedwith a plurality of slots each extending lengthwise of said stack andeach extending inwardly from an outer peripheral edge of said stack,said slots being spaced from each other peripherally of said stack, aconductor member of non-magnetic material positioned in each of saidslots in magnetically inductive relation to said magnetic laminationsand adapted to be connected in circuit with said conductor means, eachconductor member including a first portion lying in an inner portion ofthe respective slot in inwardly spaced relation to the outer peripheryof said slot, and a second portion lying in the respective slotoutwardly of said first portion and nearer the outer periphery of saidslot, said first portion being of substantially greater cross-sectionalarea than said second portion, whereby the smaller cross-sectional areaof said second portion presents an increased resistance to highfrequency currents flowing in said second portion.
 18. An apparatus forconnection in circuit with an electrical conductor means tosubstantially attenuate high frequency electrical voltages and currentsbut which transmits electrical voltages and currents of normal powerfrequency or direct current without substantial attenuation thereof,comprising a stack of magnetic laminations, said stack of magneticlaminations being provided with a plurality of slots each extendinglengthwise of said stack and each extending inwardly from an outerperipheral edge of said stack, said slots being spaced from each otherperipherally of said stack, and an electrical conductor member ofnon-magnetic material positioned in each of said slots in magneticallyinductive relation to said magnetic laminations, the conductor memberspositioned in the plurality of slots being connected in series with eachother and in circuit with the electrical conductor means.
 19. Anapparatus for connection in circuit with an electrical conductor meansto substantially attenuate high frequency electrical voltages andcurrents but which transmits electrical voltages and currents of normalpower frequency or direct current without substantial attenuationthereof, comprising a stack of magnetic laminations, a slot extendinginwardly and lengthwise of said stack from an outer peripheral edge ofsaid stack, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic laminations, said conductor member being adapted to beconnected in circuit with said conductor means, said conductor memberincluding a first portion lying in an inner portion of said slot ininwardly spaced relation to the outer periphery of said slot and asecond portion lying in said slot outwardly of said first portion andnearer the outer periphery of said slot, said first portion being ofsubstantially greater cross-sectional area than said second portion,whereby the smaller cross-sectional area of said second portion presentsan increased resistance to high frequency currents flowing in saidsecond portion, and a narrow neck-like conductor portion connecting saidfirst portion and said second portion along substantially the entirelength of said first and said second portions.
 20. An apparatus forconnection in circuit with an electrical conductor means tosubstantially attenuate high frequency electrical voltages and currentsbut which transmits electrical voltages and currents of normal powerfrequency or direct current without substantial attenuation thereof,comprising a stack of magnetic laminations, a slot extending inwardlyand lengthwise of said stack from an outer peripheral edge of saidstack, and an electrical conductor member of non-magnetic materialreceived in said slot in magnetically inductive relation to saidmagnetic laminations, said conductor member being connected in circuitwith said conductor means, said conductor member including a firstportion lying in an inner portion of said slot in inwardly spacedrelation to the outer periphery of said slot and a second portion lyingin said slot outwardly of said first portion and nearer the outerperiphery of said slot, said first portion being of substantiallygreater cross-sectional area than said second portion, whereby thesmaller cross-sectional area of said second portion presents anincreased resistance to high frequency currents flowing in said secondportion, said first portion and said second portion being separated byan air gap along a substantial part of the length of said first portionand said second portion, corresponding ends of said first portion andsaid second portion being conductively connected to each other.
 21. Anassembly of damping devices for attenuating high frequency transientphenomena for connection in circuit with an electrical transmissionline, each damping device comprising an electrical conductor memberextending lengthwise thereof, said assembly comprising a supportingframe member, stand-off insulator means supporting and spacing saidframe member relative to a supporting surface, first and secondstand-off insulator members positioned in longitudinally spaced relationto each other along said frame member, a first damping device supportedcontiguous the respective opposite ends thereof by said first and saidsecond stand-off insulator members, means adapted to conductivelyconnect one end of said first damping device in series with saidelectrical transmission line, said one end of said first damping devicebeing supported by said first stand-off insulator member, a firstconductive spacer member, said first conductive spacer member beingsupported on and substantially in axial alignment with said secondstand-off insulator member, a third stand-off insulator member supportedon and substantially in axial alignment of the said first stand-offinsulator member, a second damping device supported at one end thereofby said third stand-off insulator member and at the opposite end thereofby said first conductive spacer member, the end of said first dampingdevice opposite said one end of said first damping device beingconductively connected to said opposite end of said second dampingdevice through said first conductive spacer member, whereby to placesaid first and said second damping devices electrically in series witheach other, and means adapted to connect said one end of said seconddamping device in circuit with said electrical transmission line,whereby said first and said second damping devices are connected inseries with each other and are adapted tO be connected in circuit withthe electrical transmission line.
 22. An assembly of damping devices asdefined in claim 21 in which said means adapted to connect said one endof said second damping device in circuit with said electricaltransmission line comprises additional damping devices connected inseries with said second damping device, the last of said additionaldamping devices being adapted to be connected to the transmission line,whereby to place said assembly in circuit with the transmission line.23. An assembly of damping devices as defined in claim 21 in which therespective damping devices are of the type comprising a stack ofmagnetic laminations and a corresponding conductor member received in aslot in each respecitve stack, the conductor members of the plurality ofdamping devices being connected in series with each other and in circuitwith the transmission line.
 24. An assembly of damping devices forattenuating high frequency transient phenomena for connection in circuitwith an electrical transmission line, said assembly comprising asupporting frame member, stand-off insulator means supporting andspacing said frame member relative to a supporting surface, and a stackof damping devices supported on said frame member in a planesubstantially normal to said supporting surface, said stack comprisingfirst and second stand-off insulator members positioned inlongitudinally spaced relation to each other along said frame member, afirst damping device supported in spaced relation to said frame memberby said first and second stand-off insulator members, means adapted toconductively connect one end of said first damping device in circuitwith the electrical transmission line, said stack comprising a pluralityof additional damping devices each supported in said plane in stackedrelation to said first damping device and to each other by acorresponding additional stand-off insulator at one end of eachrespective damping device and by a corresponding conductive spacer at anopposite end of each respective damping device, the relative position ofthe corresponding stand-off insulator and of the correspondingconductive spacer being reversed for successive damping devices in thesaid stack whereby each corresponding conductive spacer establishes aconductive connection between successive damping devices to placesuccessive damping devices electrically in series with each other, andwhereby to place the plurality of damping devices of the stack in serieswith each other, and means adapted to connect the terminal end of thelast damping device in said stack in circuit with the electricaltransmission line.
 25. An assembly of damping devices as defined inclaim 24 in which the means adapted to connect one end of the stack ofdamping devices in circuit with the electrical transmission linecomprises at least one additional stack of damping devices as defined inclaim 18 whereby to place said at least one additional stack of dampingdevices in series with said first-mentioned stack and in circuit withsaid transmission line.